Polymeric roof sheeting is used as single ply roofing membrane for covering industrial and commercial flat roofs. Such membranes are generally applied to the roof surface in vulcanized or cured state.
Because of outstanding weathering resistance and flexibility, cured EPDM based roof sheeting has rapidly gained acceptance. While this material is suitable for covering the roof and, it is capable of withstanding some traffic, it is customary to apply walkway pads, comprising rubber materials, directly onto the membrane defining a traffic pattern to areas of the roof to which travel is required. Walkway pads are known and accordingly, the present invention applies to all such pads.
Walkway pads are currently applied to roofing membranes and other forms of roof covering material with the use of liquid adhesives or tape adhesives which are applied to the walkway pad in the field, prior to installing the walkway pad on the roof surface. This method involves cleaning and/or priming the walkway pad just prior to field applying the liquid or adhesive tape to pad. The field applied adhesive keeps the walkway pad in place on the roof surface, and the walkway pad serves to protect the roof system/membrane from foot traffic. Attendant this method is the emission of volatile organic compounds, or VOC's, released during cleaning and priming of the walkway pad. Moreover, there is a fair amount of labor necessitated with this method of application.
Tape compositions are known and are used not only to adhere walkway pads, but also for seaming roofing membranes together. As an example, uncured polymeric tapes containing no vulcanizing agents, i.e., non-curable tapes, have been developed.
Another type of adhesive composition often used for joining roofing sheet membranes together is that which is initially unvulcanized but which contains curatives so as to be vulcanizable. These adhesives, commonly referred to as rooftop curable adhesives, are typically used in the form of a preformed tape to bond sheet membranes and the like together.
In order to provide adhesion and a watertight seal between the tape and the rubber sheeting upon contact, these adhesive tapes typically include a tackifying additive compatible with the rubber employed such as polybutene. It has been found that polybutene, when used with a butyl rubber composition, provides an adhesive tape having sufficient surface tack and "quick-grab" as well as adequate green strength for use in adhering roofing sheet membranes together.
Accordingly, heretofore, most pressure sensitive adhesives used to join rubber roofing membranes together included a rubbery polymer composition based on butyl rubber or butyl rubber blended with various amounts of EPDM. The cured adhesive also included a cure package, typically based upon the use of a sulfur, peroxide or quinoid crosslinking system.
For example, Chiu U.S. Pat. Nos. 4,588,637, 4,855,172 and 5,095,068 disclose adhesive compositions, prepared in the form of a cured adhesive tape, which comprises butyl rubber-based compositions made by compounding a butyl rubber, a curing agent for the butyl rubber, carbon black, and a compatible tackifying additive.
Metcalf et al. U.S. Pat. No. 4,601,935 discloses a seaming tape comprising a carbon black-reinforced, compounded, lightly cured blend of a butyl rubber and a polyisobutylene. The seaming tape serves to adhere the primer-coated seam edges of EPDM membranes together.
Briddell et al. U.S. Pat. No. 5,242,727 discloses a cured adhesive tape composition which includes substantially equal amounts by weight of a rubbery polymer comprising a blend of EPDM, a halogenated butyl rubber or a halogenated isobutylene-based copolymer and polyisobutylene, a compatible tackifying additive and a compatible accelerator/cure package for the rubbery polymer blend.
It is clear that all of the above adhesive tape compositions include butyl rubber (IIR). The term "butyl rubber" as used herein is intended to include copolymers of isobutylene and isoprene as well as other rubbery copolymers comprising at least 50 percent by weight of an isoolefin having 4 or more carbon atoms and 50 percent or less by weight of an open chain conjugated diolefin having from 4 to 8 carbon atoms. "Butyl rubber" is intended to also include halogenated butyl rubber, such as chlorobutyl or bromobutyl rubber, as well as those types of butyl rubber in which conjugated diene functionality has been added in the linear backbone at the diolefin units, such as more particularly described in U.S. Pat. No. 3,816,371.
Some patents have recognized the use of EPDM in tape compositions. For example, Fujuki et al. U.S. Pat. No. 4,379,114 discloses a curable tape which may include a vulcanizable, but unvulcanized EPDM rubber, butyl rubber, or a blend thereof. The curable tape may further include a vulcanizing agent and accelerator, a softening agent, and other ingredients such as fillers and the like.
Kakehi et al. U.S. Pat. No. 4,404,056 discloses a cold-vulcanizable adhesive tape having a Mooney viscosity of from about 5 to 25 and which includes a rubbery polymer comprising EPDM, butyl rubber or a blend thereof, as well as a vulcanizing agent, a vulcanization accelerator, an adhesive (tackifying) agent and a softening agent.
Westley U.S. Pat. No. 4,581,092 discloses a preformed adhesive tape composition comprising EPDM or halogenated butyl rubbers, at least one polyisocyanate, a low-temperature and a high-temperature tackifying additive, and at least one curing agent.
While the use of various adhesive tapes to adhere walkway pads to roofing membranes is known, the art has not heretofore recognized self-adhering walkway pads or a method for applying walkway pads to roofs involving the use of self-adhering walkway pads.